Pierce A. Paul was born and raised in Guyana, South America. He earned his undergraduate degree in agronomy and his M.S. degree in plant pathology from the Federal University of Viçosa, Brazil, under the guidance of Francisco Xavier Ribeiro do Vale. In 2003, he graduated with a Ph.D. degree in plant pathology, with a minor in statistics, from Iowa State University, under the guidance of Gary Munkvold. In the summer of 2003, he joined Pat Lipps and Larry Madden in the Department of Plant Pathology at The Ohio State University (OSU) as a postdoctoral researcher. He became a research scientist in 2005, and in August 2006, Paul joined the faculty of OSU, with research and extension responsibilities for small grain and maize diseases. In a short 5 years, Paul has made major research advances on two major diseases of field crops, gray leaf spot of maize (Cercospora zeae-maydis) and Fusarium head blight of wheat (FHB or scab, caused by Fusarium graminearum [Gibberella zeae]). As part of his Ph.D. research, he developed prediction models for gray leaf spot based on data collected through detailed statistical surveys of commercial fields over several years, coupled with state-of-the-art data-analytical methods. He used artificial-neural-network, logistic regression and classification-and-regression-tree approaches to develop risk models, which can be used before planting (to make hybrid selection and evaluate the risk of growing certain hybrids or to decide even if it is worth growing maize in a given year and location) or during the season (to make fungicide application decisions). With the increased acreage of maize in the Midwest and the higher unit prices for grain, these risk models have now taken on greater significance.
Since moving to OSU, Paul has made several key contributions to our understanding of the epidemiology and control of FHB, perhaps the most economically important disease of any crop in the United States over the last two decades. Because of the economic impact of FHB, several scientists from around the United States, under the auspices of the U.S. Wheat and Barley Scab Initiative, have been studying disease epidemics (and toxin production) in relation to the environment and crop characteristics and to disease (and toxin) management. Paul has established himself as a key member of the epidemiology and management teams, using his expertise in statistics to assist in the coordination of multistate projects, organization of data, and quantitative synthesis of research findings. One highly significant contribution is his use of meta-analysis to combine results from more than 150 studies (collected over a decade) to characterize the relationship between disease intensity measurements and resulting deoxynivalenol (DON) levels in harvested grain. Numerous instances of high variability and uncertainty in this relationship have been reported, as well as conflicting results between studies, with no general consensus on whether DON could even be predicted from field symptoms of FHB. Through the meta-analysis, Paul and colleague Madden showed that a significant positive and linear relationship between “disease index” and DON exists; the strength of the relationship (precision) was greater for spring wheat compared with winter wheat; the mean DON level was higher for spring than for winter wheat at a given level of disease; DON contamination may exist even when visible disease intensity is 0; and a very high variability in the relationship between FHB index and DON occurs. Based partly on these results, a new series of coordinated studies have been initiated in multiple states to elucidate the causes of the variation.
Paul has been at the forefront of the application of meta-analysis and other statistical methods for addressing problems in plant pathology. He and collaborators have used meta-analysis to characterize the effects of triazole fungicides on FHB and DON, based on data from more than 100 studies from the last decade. Results clearly demonstrated the significant degree of control that can be obtained; the poorer control of DON compared with disease symptoms; the better control for spring than for winter wheat; and also the high variation in degree of control. Spores of the FHB pathogen had previously been shown to be wind disseminated within and between wheat canopies. However, together with former OSU postdoc S. El-Allaf, Paul showed that spores also are routinely splashed dispersed within canopies during rain episodes and that rain splash is sufficient to transport spores to the wheat spikes where infection can occur. A significant relationship between rain intensity and spore transport was documented. Based on these results, both wind and rain-splash dispersal mechanisms must be considered in determining the risk of the disease. In additional research based on data collected in more than 8 years as part of the national scab initiative, he showed that there is a significant relationship between spore density on wheat spikes and profiles of atmospheric moisture, temperature, and rainfall over 8-day periods, although the variability is high. This result depended on the unique use of polynomial distributed lag regression analysis coupled with linear mixed model analysis. In other research, Paul, together with OSU colleagues, have characterized the relationship between field severity (“disease index”) and incidence of FHB using a novel nonlinear model and have shown how the precision of the predicted index is related to the precision of the sampled incidence. This work is useful to improve understanding of population development and spread of FHB in wheat at different scales and to develop sampling schemes based on relatively easy-to-measure incidence, with a subsequent prediction of field severity using the model.
Paul is a very productive scientist, with 15 peer-reviewed journal articles in the last 4 years. He is very active nationally, currently serving as chair of the APS Epidemiology Committee and the USDA Technical Committee/project NCERA184, “Management of Small Grain Diseases.” He has been an invited speaker at two national conferences in the last 3 years. He also plays a critical role in OSU’s wheat breeding programs, screening for resistance to multiple diseases.
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